Air plug gage construction



Aug 24, 1965 J, c gs 3,201,974

AIR PLUG GAGE CONSTRUCTION Filed Dec. 8, 1960 My ggggg & fiwqtogwyUnited States Patent 3,201,974 AER PLUG GAGE CGNSTRUCTKON Walter J.Croshier, Hyde Park, N.Y., assignor to Standard Gage Company, inc,Poughkeepsie, N.Y., a corporation of New York Fiied Dec. 8, 1960, Ser.No. 74,599 2 Qiairns. (Cl. 73-379) The present invention relates to pluggages and especially to plug gages in which the gaging operation isperformed by flow of air from a diametrically arranged pair of orifices.As is well known in plug gages of the air type orifices are provided bydiametrically opposed nozzles,

1 the faces of which are cylindrical and at the ends of a dius necessaryas between the nozzle faces on the one hand and the cylindrical body ofthe gaging plug on the other. One method which has been utilized toproduce high quality long wearing air plug gages was to first machinethe gage to give the proper nozzle air orifices and escape grooves andto then cylindrically grind the plug, on centers, to establish theproper diameter across the nozzles. Thereafter the nozzle faces weremasked and the plug body plated with hard chrome to a thickness somewhatgreater than the required radial difference between the nozzle and thebody. This radial difference is normally approximately 0.0015 inch. Thebody was then ground to a desired final diameter leaving a smooth layerof chromium for wear resistance.

As will be obvious in the case when the radial difference between thenozzle and body is 0.0015 inch, the body in its finished grinding willbe ground to a diameter 0.003 inch greater than the diameter resultingfrom the first grinding prior to chromium plating. The time required forthe masking, heavy plating and subsequent grinding add materially to thecost of producing such a plug gage.

Another method of producing plug gages of the general type discussedabove has been that known as rock grinding. In this method a very smallgrinding Wheel making end contact grinds the nozzle faces one at a timeto the desired dimension, this being achieved by oscillating or rockingthe workpiece slightly on its centers to thus produce the cylindricalfaces of the nozzles only. By this means the plating is avoided but thenecessity for exactly determining the degree of oscillation and formaking the two nozzles on a true cylindrical diameter and exactly thesame depth below the body surface while obtaining a good finish on thenozzle faces renders this method also quite costly.

y In a third method of producing plug air gages the plug is ground totwo diameters, the nozzle faces being part of a shallow circumferentialrelief band just wide enough to include the nozzles. This method isconsiderably cheaper than the two methods outlined hereinabove andproduces a gage which is satisfactory for many types of gagingoperations. Except for the fact that the gage is not chromium plated itis in general comparable to those formed by the other methods. Becauseof the lack of platingit is of course more subject to wear and is genofthe third method in a form in which the limitations as to conditions ofuse are overcome. The limitations mentioned broadly arise from the factthat with a circumferential relief band it is ditficult if notimpossible to avoid damage to the nozzles when a workpiece of relativelysmall axial extent is to be gaged, since when this is the case tippingof the workpiece will cause an edge of that workpiece to come intocontact with and damage the nozzle faces.

My invention modifies the construction of this third type of gage byutilizing a relief groove which, instead of extending circumferentially,extends in a oval about the cylindrical plug, that is, the grooveextends about the cylindrical plug at an angle to a circumference whichangle is preferably, but not necessarily, 45

It is an object of my invention to provide a relatively inexpensive airplug gage which at the same time eliminates the possibility of nozzledamage even when gaging a workpiece which is of relatively small extentin the axial direction.

It is another object of the invention to provide an air plug gage havinga relief band which leaves a maximum surface of the body diameter in aplane perpendicular to the plug axis and extending through the nozzles.

Other objects and features of the invention will be apparent when thefollowing description is considered in connection with the annexeddrawings, in which,

FIGURE 1 is a top plan view of a plug gage in accordance with myinvention;

FIGURE 2 is a side elevational view of the gage of FIGURE 1; and

FIGURE 3 is a transverse cross-sectional view of the gage of thepreceding figures, the view being taken on the plane of the line 1-1 ofFIGURE 1.

Referring now to the drawings, the air plug 10 is, in a customarymanner, formed of a cylindrical surface 11 having nozzles 12 formedgenerally centrally thereof in an axial direction and at opposite endsof a diameter. The nozzles 12 comprise a central orifice 13 surroundedby land 14 which is in turn surrounded by a shallow circumferentialgroove 15.

As is customary, a central air passage extends axially through the plugas indicated at 16, this passageway communicating with the twopassageways 17 and 18 which in turn communicate with the orifices 13. Asis well known, the passageway 16 is connected to a source of airpressure through a pressure gage so that the gage reading determines thepressure drop resulting from flow of air through the orifices andthrough the restricted passageways formed by the cylindrical nozzlefaces and the adjacent walls of the bore being gaged.

Extending longitudinally of the plug 10 are the air escape grooves 20each of which communicates with the corresponding circumferential groove15, thus permitting air flow to be regulated only by the restrictionabove mentioned and not otherwise.

In order to grind the nozzle faces so that they form part of acylindrical surface of slightly lesser diameter than that of the body ofthe gage, a relief groove 21 is produced, this groove forming a bandpreferably at 45 to the plane of a cylindrical diameter and includingthe nozzle faces, that is, the land 14 between the circular groove 15and the orifice opening 13. This relief groove 21 may be produced in anumber of ways, but it is preferable that a grinding wheel be mounted onan axis parallel to the centers of the plug body 11 and that as the bodyis rotated on center the grinding wheel rotates on its center and at thesame time reciprocates from the point 21 to the point indicated at 22.When the reciprocatory movement and the rotation of the plug body areproperly synchronized the skewed groove 21 will be produced and 3 asindicated the nozzle facesbwill lie on the cylindrical surface of thatgroove and be the desired amount beneath the surface of the plug body. I7

As Will be readily apparent, a piece to be gaged which is axiallyrelatively narrow is nevertheless wellsupported by the plug body andcannot be tipped so that an edge thereof engages and damages either ofthe nozzle faces. On the other hand, when similar relief grooves wereprovided Whichextended circumferentially of the gage body, an axiallynarrow workpiece might, in the absence of extreme care, be so tipped asto strike one of the nozzle faces and cause damage thereto. 'When it isrealized that in'order for the gage to be usable and accurate, thenozzlefaces must be accurately spaced-from the gage body surfaceby-amounts in the range of 0.0015 inch or less, it becomes clear thatany damage to these nozzle faces destroys .the utility of the gage. Thusby the relatively simple provision of a groove which 'is inclined to thediametrical plane of the nozzles rather than being centered about thatplane, the possibility ofdamaging thenozzles and destroying the utilityof the gage is substantally eliminated. 1

Moreover, as has been indicated, the cost of producing a gage havingthis inclined groove, is materially less than the cost of gages producedby methods requiring masking and plating and it is, in fact,substantially the same as the cost of producing the circumferentialgroove which presents the possibility of damage as hereinabove de-.

scribed. J

While I have described a preferred embodiment of my invention, it willbe understood that I Wish to be limited not by the foregoingdescription, but solely by the claims granted to me.

What is claimed is: a

1. In an air plug gage, in combinatiomla cylindrical plug body, a bandof lesser diameter than said body ex tending completely around said bodyat an angle to the plane of a cylindrical diameter of said body, a pairof nozzles in said plug body, saidnozzles comprising apertures openinginto said band at diametrically opposite points thereof and acirculargroove concentric with each said aperture, and a pair of longitudinalgrooves, each said longitudinal groove communicatingwith one of saidconcentric grooves'whereby air may escape from said apertures. r

2. In an airplug gage, in combination, a cylindrical plug body, a bandof lesser diameter than said body extending completely around said bodyat an angle of 45 7 to the plane of a cylindrical diameter of said body,a pair tures.

of nozzles in said plug body, said nozzles comprising apertures openinginto said band at diametrically opposite points thereof and a circulargroove concentric with each aperture, and a pair of longitudinalgrooves, each said longitudinal groove communicating with one of saidconcentric grooves whereby airmay escape from said aper- ReferencesCited by the Examiner UNITED STATES PATENTS 2,360,705 10/44 Moore73-37.9 2,412,413 12/46 Moss 33 2,457,401 12/48 Rupley 73-379, 2,706,3394/55 Aller 73 37.9 2,746,287 I 5/56 Tinker 73-379 2,963,900 12/60Kuebler 33

2. IN AN AIR PLUG GAGE, IN COMBINATION, A CYLINDRICAL PLUG BODY, A BANDOF LESSER DIAMETER THAN SAID BODY EXTENDING COMPLETE AROUND SAID BODY ATAN ANGLE OF 45* TO THE PLANE OF A CYLINDRICAL DIAMETER OF SAID BODY, APAIR OF NOZZLES IN SAID PLUG BODY, SAID NOZLES COMPRISING APERTURESOPENING INTO SAID BAND AT DIAMETRICALLY OPPOSITE POINTS THEREOF AND ACIRCULAR GROOVE CONCENTRICALLY OPPOSITE APERTURE, AND A PAIRE OFLONGITUDINAL GROOOVES, EACH SAID LONGITUDINAL GROOVE COMMUNICATING WITHONE OF SAID CONCENTRIC GROOVES WHEREBY AIR MAY ESCAPE FROM SAIDAPERTURES.